Did the twelve disciples ever preach to the Gentiles?
No, the twelve disciples never preached to the Gentiles. Their witness was limited to Jerusalem, Judea, and Samaria. Scripture shows no instance of those twelve having a ministry among Gentiles because Israel's rejection of the King removed that opportunity.
Les teaches that the twelve disciples never went to the nations of the world. The commission in Acts 1:8 was fulfilled only as far as Samaria, as seen when Philip went to Samaria in Acts 8, and Samaria heard the word. But the twelve never had a ministry among Gentiles. Les challenges anyone to show a single time in Scripture where those twelve disciples did so—they didn't. The reason given is that Israel never accepted the King, so that opportunity was taken from them because of Israel's rejection.
But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth.
More Questions
Did the first believers start preaching the gospel around the world right after Pentecost?
Reading Acts 1:8 alongside the Great Commission in Matthew can make it sound as though the Jewish believers would start going around the world preaching immediately after the Holy Spirit came, but they did not.